1. Field of the Invention
The present invention relates to a vehicle and a method for controlling an engine in a vehicle, and more particularly, to a vehicle having an engine and an electric machine operable to provide torque to drive the vehicle.
2. Background Art
In an effort to increase fuel economy, decrease fuel consumption, and decrease exhaust emissions from vehicles, a number of alternative vehicle types are becoming increasingly popular. For example, a hybrid electric vehicle (HEV) that utilizes an internal combustion engine and one or more electric motors to provide torque to power the vehicle, provides an alternative to conventional vehicle types which rely exclusively on an engine to drive the vehicle. In some HEV's, the engine may be automatically stopped whenever it is not needed for such tasks as powering the vehicle, charging a battery, or providing power to operate one or more vehicle systems. Control of the engine in such a vehicle, including the selective starting and stopping of the engine, may be automatically handled by a control system. Therefore, anytime the vehicle is being operated, the engine may or may not be running, depending on the particular requirements of the vehicle.
The selective and automatic starting and stopping of an engine in an HEV, although useful to reduce fuel consumption and exhaust emissions, may present particular challenges to a service technician who needs the engine to run continuously for some period of time while a diagnostic or repair procedure is taking place. One attempt to deal with this situation is discussed in U.S. Pat. No. 6,131,538 issued to Kanai on Oct. 17, 2000. Kanai discusses an apparatus for controlling the engine in an HEV, including operation of the engine in an inspection mode. In order to facilitate the inspection mode, a check wire is applied to a diagnosis connector to connect a pair of predetermined electric terminals to each other. The connection of these terminals provides an output signal that facilitates putting the engine in an inspection mode—a mode which may be characterized by continuous operation of the engine.
One limitation of the apparatus described in Kanai, is the need to use an external device, such as the check wire, to facilitate placing the engine in the inspection mode. It would be more convenient, and therefore desirable, if an HEV were equipped to operate an engine in an inspection mode by using only existing vehicle systems, thereby eliminating the need for any external devices. In addition, it may desirable to provide other inspection modes, wherein the engine is operated under some other predetermined set of conditions that were different from the normal operating conditions. For example, in order to check the compression of the cylinders in the engine, it is necessary to crank the engine—i.e., move the pistons up and down within their respective cylinders—while prohibiting starting of the engine.
Such an inspection mode is described for a hybrid electric vehicle in Toyota Prius Repair Manual, Vol. 2, Pub. No. RM778U2, Copyright 2000 Toyota Motor Corporation. The compression inspection routine provides a cranking mode during which cylinder compression can be measured. To facilitate the compression inspection, a hand-held tester is connected to an input port and a cranking mode is chosen on the hand-held tester. This method also requires the use of a device external to the vehicle to facilitate the testing. It would be desirable to facilitate this type of inspection mode in an HEV without the need to use external devices which may add cost and complexity to the procedure.